Tackiness tester

ABSTRACT

An apparatus, for determining the degree of tackiness of a surface of a body, comprises a closed chamber with inlet and outlet openings; a support for the body within the chamber; a fan for providing an airflow directed toward the surface of the body within the chamber; a powder dispenser for releasing powder into the path of the airflow upstream of the body surface, the powder being adapted to be carried by the airflow thereby to permit the powder to impinge against the body surface; whereby the amount of powder adhering to the body surface after a period provides a measure of tackiness of the surface.

This is a division of application Ser. No. 07/641,307 filed Jan. 15,1991.

FIELD OF THE INVENTION

The present invention relates generally to an apparatus for providing ameasure of degree of tackiness of a surface and particularly to atackiness tester employing a dusting chamber.

BACKGROUND OF THE INVENTION

A circuit board, before circuit components are connected onto it, istypically coated with flux, which aids in the soldering of the circuitcomponents onto the board. After the components are soldered, thecircuit board is typically washed with fluid containing CFC(Chlorinatedfluorocarbon), such as FREON, to remove any excess flux.Because CFC is known to be harmful to the environment, it is desiredthat the use of CFC be eliminated, while maintaining the reliability andquality of the circuit board.

The use of CFC may be eliminated if low solids flux is used and theamount that is deposited on the circuit board is carefully controlledsuch that only the required amount necessary for the soldering processis deposited on the circuit board. To maintain quality control, it isnecessary to have a means for objectively monitoring the consistency ofthe flux deposit process. One such means is an apparatus, in accordancewith the present invention, for measuring the degree of tackiness of theflux coated circuit board.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide anapparatus for monitoring the proper amount of flux deposited on acircuit board such that excess flux is substantially eliminated, therebyeliminating washing with CFC fluid.

It is another object of the present invention to provide a tackinesstester that provides a consistent means for determining the degree oftackiness of a flux coated circuit board.

It is still another object of the present invention to provide atackiness tester that provides a standardized means for gauging therelative amount of deposited flux between a number of circuit boards.

It is yet another object of the present invention to provide a tackinesstester that is relatively simple and inexpensive to manufacture.

In summary, the present invention provides a tackiness tester that isdesigned to eliminate the use of CFC in circuit board assembly byproviding a means for monitoring the amount of flux deposited on thecircuit board such that only the amount needed is used and any excessamount is avoided.

These and other objects of the present invention will become apparentfrom the following detailed description.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a perspective schematic view of a tackiness tester accordingto the present invention.

FIG. 2 is a top view of the tackiness tester shown in FIG. 1, withportions shown in phantom lines.

FIG. 3 is a cross-sectional view taken along line 3--3 in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of a tackiness tester A according to the present inventioncomprises a closed chamber 2 with an opening 4 and a hingedly operabledoor 6 for access into the chamber 2, as best shown in FIG. 1. A lock 8permits the door 6 to be in the closed position during operation.

A fan housing 10 is operably associated with one side of the chamber 2and communicates with an inlet opening 12 into the interior of thechamber 2. An electric fan 14 is operably secured within the housing 10.An outlet opening 16, defined by a collar 18, is disposed on an oppositeside of thechamber 2 relative to the inlet opening 12. A duct 20connects the outlet opening 16 with the inlet opening 12 andadvantageously provides a return path for the airflow 21 when the fan 14is operating, as best shown in FIG. 3.

A storage bin 22 for powder 24 is disposed adjacent and above the fan14, as best shown in FIG. 3. The bin 22 has a hingedly mounted bottomdoor 26,which is operated such that it is alternately moved about itshinge line 27to discharge the powder 24, as generally indicated at 29,into the airflow 21 generated by the fan 14, as best shown in FIG. 3.

A rod 30 is loosely connected at its one end to the door 26 and at itsother end to a connecting rod 30. A portion 31 of the rod 28 protrudesoutside the chamber 2 through a slot 32 which remains closed by means ofaflexible cover 34. The rod 30 is pivotally connected to the rod 28 atpivot36. The other end of the rod 30 is pivotally connected to a crank38 that is driven by an electric motor 40.

Movement of the rod 28 during operation causes the release of the powder24into the airflow 21. A person of ordinary skill in the art willunderstand that there are other means for causing the powder 24 to bereleased to theairflow 21.

The bin 22 is provided with a hingedly operated cover 41 at its topportionfor reloading with the powder 24.

A support 42, disposed within the chamber 2 substantially transverse totheairflow 21, provides supporting means for a test board 44 (shown indashed lines) such that its surface 45 is preferably oriented verticallyand exposed directly to the airflow 21. A person of ordinary skill inthe art will understand that there are other means for supporting thetest board 44 within the chamber 2.

OPERATION

In operation, the test board 44 to be tested for tackiness with itssurface45 coated with flux is positioned within the chamber 2 andsecured in the support 42. The board 44 is preferably positioned suchthat the surface 45is oriented vertically, as best shown in FIG. 3. Thevertical orientation of the surface 45 advantageously permits any excesspowder to drop to the bottom of the chamber 2. The test board isdisposed within the chamber 2 such that the surface 45 will be in thedirect path of the airflow 21.

The fan 14 is then energized, generating the airflow 21, which follows apath from the inlet 12 to the outlet 16. A person of ordinary skill intheart will understand that there are other means of generating theairflow 21, such as compressed air, etc.

The motor 40 is next turned on. The crank 38, which is operablyconnected to the motor 40, rotates and causes the connecting rod 30 tomove the end portion 31 of the rod 28 along the slot 32, imparting avibratory motion to the rod 28. The movement of the rod 28 vibrates thedoor 26 and therebyagitates the powder 24 at the bottom of the bin 22.The agitation of the door 26 and the contacting powder causes therelease of the powder 24 as generally indicated by 29 into the airstream 21, as best shown in FIG. 3.The bin 22 is advantageously disposedabove the airflow 21 such that the powder 24 when released falls bygravity into the airflow 21. The powder 24 is then carried by theairflow 21, impinging against the surface 45 of the test board 44. Someof the powder carried by the airflow 21 will adhere to the surface 45,the adhering amount being dependent on the degree of tackiness of thesurface.

The powder laden airflow 21 is advantageously recirculated through theduct20. The fan 14 and the motor 40 are operated for a specified time.

The board 44 is weighed before being placed in the chamber 2 and isreweighed after it has been subjected to the powder laden airflow 21. Anindication of the degree of tackiness of the board 44 is provided by thepercentage weight amount of the powder 24 that adheres to the board. Thegreater the percent weight of the powder sticking to the board, thegreater the degree of tackiness of the board relative to another boardwith a lesser amount of adhering powder.

A person of ordinary skill in the art will appreciate that the tackinesstester A provides a reproducible and consistent method for gauging thedegree of tackiness of the board 44. The tackiness tester A provides astandardized means for monitoring the degree of tackiness of a number ofcircuit boards after they are coated with flux in a flux depositprocess. Appropriate adjustment to the process may be made based on theresults provided by the tackiness tester A.

The powder 24 is preferably calcium carbonate, which is considerednon-toxic. The particle size of the powder is preferably approximately90 microns (170 mesh). The size of the particles is advantageously nottoo fine so that they would stick to almost any surface and are not toolarge and heavy so that they would not stick to the surface at all.

While this invention has been described as having preferred design, itis understood that it is capable of further modification, uses and/oradaptations of the invention following in general the principle of theinvention and including such departures from the present disclosure ascome within known or customary practice in the art to which theinvention pertains and as may be applied to the essential features setforth and fall within the scope of the invention or the limits of theappended claims.

We claim:
 1. An apparatus for determining the degree of tackiness of asurface of a body, comprising:a) a completely enclosed chamber havinginlet and outlet openings for providing an airflow; b) a support holderfor positioning the body within said chamber such that a surface isdisposed vertically and transversely to an airflow; c) means forproviding the airflow directed toward the surface of the body withinsaid chamber; d) means downstream of said airflow-providing means fordispensing powder into the path of the airflow upstream of the bodysurface, the powder being adapted to be carried by the airflow therebyto permit the powder to impinge against the body surface; e) whereby theamount of powder adhering to the body surface after a period provides ameasure of tackiness of the surface.
 2. An apparatus as in claim 1,wherein:a) said positioning means is adapted to secure a planar bodysubstantially transverse to the airflow.
 3. An apparatus as in claim 1,wherein:a) said airflow means includes a fan operably associated withsaid inlet opening.
 4. An apparatus as in claim 1, and furthercomprising:a) a duct operably connected to said inlet and outletopenings.
 5. An apparatus as in claim 1, wherein said dispensing meanscomprises:a) a bin; b) a pivotable door operably associated with abottom portion of said bin and disposed within said chamber above theairflow; and c) means for alternately pivoting said door thereby torelease the powder within said bin into the airflow.
 6. An apparatus asin claim 5, wherein:a) said pivoting means includes a rod and a crank;b) one end of said rod is loosely connected to said door and the otherend of said rod is operably connected to said crank; c) whereby movementof said crank causes said door to alternately pivot, thereby releasingthe powder within said bin into the airflow.
 7. An apparatus fordetermining the degree of tackiness of a surface of a body,comprising:a) a completely enclosed chamber having inlet and outletopenings for providing an airflow; b) a support holder for positioningthe body within said chamber such that a surface is disposed verticallyand transversely to an airflow; c) means disposed in said inlet openingfor establishing the airflow directed toward the surface of the bodywithin said chamber; d) means disposed above the airflow for dispensingpowder into the path of the airflow upstream of the body surface, saidpowder being adapted to be carried by the airflow thereby to permit thepowder to impinge against the surface; e) whereby the amount of powderadhering to the surface after a period provides a measure of tackinessof the surface.
 8. An apparatus as in claim 7, wherein:a) saidpositioning means is adapted to secure a planar body substantiallytransverse to the airflow.
 9. An apparatus as in claim 8, wherein:a)said airflow means includes a fan operably associated with said inletopening.
 10. An apparatus as in claim 9, and further comprising:a) aduct operably connected to said inlet and outlet openings.
 11. Anapparatus as in claim 10, wherein said dispensing means comprises:a) abin; b) a pivotable door operably associated with a bottom portion ofsaid bin and disposed within said chamber above the airflow; and c)means for alternately pivoting said door thereby to release the powderwithin said bin into the airflow.
 12. An apparatus as in claim 11,wherein:a) said pivoting means includes a rod and a crank; b) one end ofsaid rod is loosely connected to said door and the other end of said rodis operably connected to said crank; c) whereby movement of said crankcauses said the door to alternately pivot, thereby releasing the powderwithin said bin into the airflow.